[2.x] ci: bump actions/checkout from 6 to 7 (#9366)

Bumps [actions/checkout](https://github.com/actions/checkout) from 6 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v6...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/dependency-graph.yml

@@ -12,6 +12,6 @@ jobs:
     name: Submit Dependency Graph
     runs-on: ubuntu-latest # or windows-latest, or macOS-latest
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - uses: sbt/setup-sbt@v1
       - uses: scalacenter/sbt-dependency-submission@v3